Changes in the glutathione (GSH) metabolism of Penicillium chrysogenum grown on different nitrogen, sulphur and carbon sources

Changes in the de novo glutathione (GSH) synthesis (GSH producing activity; GPA), in the gamma-glutamyltranspeptidase (gamma GT) and GSH reductase (GR) activities as well as in the GSH pools were measured in a high beta-lactam producing strain of Penicillium chrysogenum in the presence of different nitrogen, sulphur and carbon sources. When (NH4)(2)HPO4 was used as a nitrogen source both the specific GPA and the specific gamma GT activity were significantly lower than those observed with Na-Glu, meanwhile nitrogen starvation increased the gamma GT activity only. Although neither the addition of ammonium ions nor the withdrawal of nitrogen sources influenced the GSH pool during a 10 h cultivation the addition of the sulphur containing amino acids cysteine (Cys) or methionine (Met) at a concentration of 20 mM increased considerably both the specific GPA and the intracellular GSH levels. Nevertheless, GPA decreased significantly when either Cys or Met was added at a three times higher concentration. When glucose was replaced by lactose as a carbon source or during carbon starvation the GPA values and the GSH concentrations were higher while the GR activities were lower than those observed with glucose. Nevertheless, no changes in either the enzyme activities or the GSH levels were detected when glucose was replaced with 2-deoxy-D-glucose or glucose together with caffeine was added to the culture media.